The “Art” of Making a Diagnosis
There truly is an art in the mental exercise of a physician making a diagnosis of the patient’s illness. In fact, I think the art really trumps the science itself in most cases. Why do I say that? It is because no two patients are the same and no two same diseases present exactly the same way nor are their courses exactly the same. It is also because lab tests are rarely or ever 100% sensitive and also 100% specific. That means that at times a lab test will miss a disease or will indicate the disease is present but actually it isn’t.
In addition to this variability, is the variability of how thoroughly the physician takes the history from a patient or the variablility of some patients who don’t remember, don’t tell or may understate or embellish their symptoms for one reason or another. Then there is the variability of how the physician performs the physical exam in terms of completeness and attention to discover and interpret pertinent physical abnormalities or lack of abnormalities. Finally, there is the variability in how the physician selects the necessary tests and how the physician interprets the results in terms of supporting or not supporting possible diagnoses. As I have suggested in previous posts, the time available to physician to do all this is also a variable. So, in fact, making a diagnosis is really an art. But it is an art that we try to teach our second year medical students before they step into their clerkship duties in the third year.
Doctors attempt to make a diagnosis through two general methods. There is the experiential “script” in which the physician has learned or by experience has observed the pattern of symptoms and physical finding that lead to a certain disease that was finally diagnosed. When the doctor sees a patient who has virtually the same pattern of symptoms, that disease is immediately brought to mind and is considered high on the list of possible diagnoses. Unfortunately, not all similar patterns represent the same disease. The other method of making the diagnosis is “analytical”. That is, moving through the symptoms and physical findings in a step wise fashion and collecting a list of diagnoses along the way, eliminating some or supporting some by additional history or physical or laboratory findings. This is a slower process than the “script” method but might end up with a more correct diagnosis.
Those who have studied the methods believe that the use of both methods together, in coming to a diagnosis of a patient, is probably the most common and more likely to produce a more rapid and correct result. The pattern of findings suggests a diagnosis that is added to the list of other diagnoses that might be developed by the analytic method and then is subjected, along with the others, to the analytic process of support or elimination.
A complication in making a diagnosis is the issue of whether the symptoms and physical findings and labs all represent a single disease or whether, in fact, the patient actually has two or several symptomatic diseases at the same time. In earlier years, a single symptomatic disease at a time was probably more common. But in the current years, where more people are living into old age when more than one ongoing disease may be present and the older people are taking more medications which have side-effects and drug interactions, the possibility of more than one illness is more likely. We teach our students to start out trying to put all the facts together in terms of one illness but they should be ready to include multiple diagnoses if all the facts don’t seem to apply to one disease and especially if the patient is elderly.
I am presenting this explanation of the diagnostic process to my blog visitors because I think it is important for them to be aware of how their physician might be thinking as their symptoms are being evaluated and what complexities from variabilities physicians face. By knowing a bit about the process, my visitors might be able to understand and judge their physicians’ behavior more realistically and see what has gone on when the doctors makes either the right or wrong diagnoses. ..Maurice.